How can we use XPath in Java PART-2?

Sample example to work with XPath

In the previous post we learned about the XPath where I mentioned about XPath nodes, XPath Constant, XPath datatypes, XPath syntax, predicates & wildcard in XPath. Now we will see, how to use XPath expressions to extract specific data from XML source document.

XPath Operators List:-

Operator	Description	Example
|	Help to compute two nodes	//name|//java-experience
or	or	salary=50000 or salary=45000
and	and	Salary>40000 and salary<60000
mod	Division reminder(modules)	9 mod 2(Reminder 1)
+	Addition	10 + 5
-	Subtraction	10 – 5
*	Multiplication	10 * 5
div	Division	10 div 5
=	Equal	Salary = 50000
!=	Not equal	Salary != 50000
<	Less than	Salary < 50000
<=	Less than or equal to	Salary <= 50000
>	Greater than	Salary > 50000
>=	Greater than or equal to	Salary >= 50000

Many inbuilt functions are available in XPath, like Accessor, String, Numeric e.t.c. For more info visit

http://www.w3schools.com/xpath/xpath_functions.asp#string

A sample XML

<?xml version="1.0" encoding="UTF-8"?>

<!DOCTYPE note SYSTEM "employee.dtd">

<employees>

      <!--Test is a comment-->

      <employee id="1234">

            <name>KUMAR GAURAV</name>

            <designation>SYSTEM ENGINEER</designation>

            <java-experience>7</java-experience>

            <salary>50000</salary>

      </employee>

      <employee id="2341">

            <name>KUMAR AADITYA</name>

            <designation>PROGRAM MANAGER</designation>

            <java-experience>15</java-experience>

            <salary>70000</salary>

      </employee>

</employees>

XPathSample.java

package com.gaurav.xpath.demo;

import java.io.IOException;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import javax.xml.xpath.XPath;

import javax.xml.xpath.XPathConstants;

import javax.xml.xpath.XPathException;

import javax.xml.xpath.XPathExpression;

import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.xml.sax.SAXException;

/**

 * @author gaurav

 *   

 */

public class XPathSample {

      /**

       * This method will help to display the XML elements when we are using NODESET constant of XPath.

       *   

       */

      public static void displayXpathResult(Object result) {

            NodeList nodes = (NodeList) result;

            for (int i = 0; i < nodes.getLength(); i++) {

                  System.out.println(nodes.item(i).getNodeValue());

            }

      }

      /**

       * This method will help to display the XML elements when we are using NODESET constant of XPath and XPath wildcard.

       *   

       */

      public static void displayXpathWildCardResult(Object result) {

            NodeList nodeList = (NodeList) result;

            for (int i = 0; i < nodeList.getLength(); i++) {

                  if (nodeList.item(i).getFirstChild() != null) {

                        System.out.println(nodeList.item(i).getNodeName() + " : \t"

                                    + nodeList.item(i).getFirstChild().getNodeValue());

                  }

            }

      }

     

      /**

       * This method will help to display the XML elements when we are using NODE constant of XPath.

       *   

       */

      private static void displayXPathResultForNode(Node node) {

            NodeList nodeListData;

            if(null != node) {

                  nodeListData = node.getChildNodes();

                for (int i = 0;null!=nodeListData && i < nodeListData.getLength(); i++) {

                    Node nod = nodeListData.item(i);

                    if(nod.getNodeType() == Node.ELEMENT_NODE)

                        System.out.println(nodeListData.item(i).getNodeName() + " : " + nod.getFirstChild().getNodeValue());

                }

            }

      }

     

      public static void main(String[] args) throws XPathException,

                  ParserConfigurationException, SAXException, IOException {

           

            // DocumentBuilderFactory is created for reading xml file

            DocumentBuilderFactory builderFactory = DocumentBuilderFactory

                        .newInstance();

           

            // We can use this below line if we want to skip dtd available in the XML file

            builderFactory

                        .setFeature(

                                    "http://apache.org/xml/features/nonvalidating/load-external-dtd",

                                    false);

            DocumentBuilder builder = builderFactory.newDocumentBuilder();

            Document document = builder.parse("src\\employees.xml");

           

           

            // Creation of XPathFactory which is required for creating XPath Object

            XPathFactory xPathFactory = XPathFactory.newInstance();

           

           

            // Creation of XPath object from XPathFactory

            XPath xpath = xPathFactory.newXPath();

           

           

            // Compiling the XPath expression for getting all employee names

            XPathExpression xPathExpr = xpath

                        .compile("/employees/employee/name/text()");

           

           

            // XPath example using NODESET CONSTANT.

            Object result = xPathExpr.evaluate(document, XPathConstants.NODESET);

            System.out

                        .println("***** All available employees are as follows : *****");

            displayXpathResult(result);

           

           

           

           

            // XPath example using NODE CONSTANT.

            System.out.println("\n***** All available employees are as follows using NODE CONSTANT : *****");

            Node node = (Node) xpath.compile("/employees/employee[@id='2341']").evaluate(document, XPathConstants.NODE);

            displayXPathResultForNode(node);         

           

           

           

           

            // get all employees salary using xpath expression in java

            NodeList nodeList = (NodeList) xpath.compile(

                        "/employees/employee/salary/text()").evaluate(document,

                        XPathConstants.NODESET);

            System.out

                        .println("\n***** All salaries for the available employees using NODESET CONSTANT : *****");

           

            for (int i = 0; i < nodeList.getLength(); i++) {

                  System.out.println(nodeList.item(i).getNodeName() + "\t"

                              + nodeList.item(i).getNodeValue());

            }

           

           

            // get only one(first) employee name using xpath expression in java

            String nodeList1 = (String) xpath.compile(

                        "/employees/employee/name/text()").evaluate(document,

                        XPathConstants.STRING);

            System.out

                        .println("\n***** Name of the first employee using STRING CONSTANT : *****");

            System.out.println(nodeList1);

           

           

            // XPath expression to use wildcard.

            Object wildCardResult = xpath.compile("/employees/employee/*")

                        .evaluate(document, XPathConstants.NODESET);

            System.out

                        .println("\n***** Displaying all element using wildcard in XPath expression : *****");

            displayXpathWildCardResult(wildCardResult);

           

           

            // XPath expression to count employee nodes in the XML source document.

            Double count = (Double) xpath.compile("count(/employees/employee)")

                        .evaluate(document, XPathConstants.NUMBER);

            System.out

                        .println("\n***** Use of Count with the help of NUMBER CONSTANT : *****");

            System.out.println("How many employees are available : " + count);

           

           

            // XPath conditional example

            Boolean flag = (Boolean) xpath.compile(

                        "count(/employees/employee[@id='2341']) > 0").evaluate(

                        document, XPathConstants.BOOLEAN);

            System.out

            .println("\n***** Use of Count with the help of BOOLEAN CONSTANT : *****");

            System.out

                        .println("Is any employee is available with the ID=1234 using BOOLEAN CONSTANT : "

                                    + flag);

      }

}

Result:-

***** All available employees are as follows : *****

KUMAR GAURAV

KUMAR AADITYA

***** All available employees are as follows using NODE CONSTANT : *****

name : KUMAR AADITYA

designation : PROGRAM MANAGER

java-experience : 15

salary : 70000

***** All salaries for the available employees using NODESET CONSTANT : *****

#text 50000

#text 70000

***** Name of the first employee using STRING CONSTANT : *****

KUMAR GAURAV

***** Displaying all element using wildcard in XPath expression : *****

name :      KUMAR GAURAV

designation :     SYSTEM ENGINEER

java-experience :       7

salary :    50000

name :      KUMAR AADITYA

designation :     PROGRAM MANAGER

java-experience :       15

salary :    70000

***** Use of Count with the help of NUMBER CONSTANT : *****

How many employees are available : 2.0

***** Use of Count with the help of BOOLEAN CONSTANT : *****

Is any employee is available with the ID=1234 using BOOLEAN CONSTANT : true